Directional Dispersion and Assignment of Optical Phonons in LiNbO3

1972 ◽  
Vol 27 (8-9) ◽  
pp. 1187-1192 ◽  
Author(s):  
R. Claus ◽  
J. Brandmüller ◽  
G. Borstel ◽  
E. Wiesendanger ◽  
L. Steffan
Keyword(s):  
Short Wavelength ◽  
Uniaxial Crystal ◽  
Optic Axis ◽  
Optical Phonons ◽  
Dispersion Theory ◽  
Phonon Modes ◽  
Phonon Wave Vector ◽  
Complete Assignment ◽  
Firm Basis ◽  
Degenerate Type

Abstract From the general polariton dispersion theory it can be shown that in an uniaxial crystal the frequencies of optical phonons * which are identical to those of the short wavelength polaritons depend on the angle Θ between the optic axis and the phonon wave vector. For Θ=0 and Θ=Π/2 the phonons are exactly transversal or longitudinal so that they can be assigned to be of totally symmetric or twofold degenerate type. Careful measurements of the directional dispersion of all phonon modes of LiNbO3 form a firm basis for a new complete assignment. 6 of the total number of 13 dispersion branches previously given in the literature had to be reassigned.

DISPERSION OF THE QUASI-CONFINED OPTICAL PHONONS IN WURTZITE GaN/AlN MULTIPLE QUANTUM WELLS

2007 ◽  
Vol 21 (25) ◽  
pp. 4407-4418
Author(s):  
WEN DENG HUANG ◽  
SHU YI WEI ◽  
YA JIE REN ◽  
YA HUI WANG
Keyword(s):  
Quantum Wells ◽  
Uniaxial Crystal ◽  
Strain Effect ◽  
Multiple Quantum ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Crystal Model ◽  
Dielectric Continuum ◽  
Dielectric Continuum Model ◽  
Confined Phonons

Within the framework of the dielectric-continuum model and Loudon's uniaxial crystal model, the dispersions of the quasi-confined optical phonons in arbitrary wurtzite multiplelayer heterostructures are solved by using the transfer-matrix method. The dispersion relations of the quasi-confined phonons are investigated for GaN/AlN single QW and coupled QWs. The confinement of the quasi-confined phonons leads to a quantization of qz, j characterized by an integer m that defines the order of corresponding quasi-confined modes. The quasi-confined modes are more dispersive for decreasing m (i.e., for decreasing qz, j, the bands formed by the dispersion curves are narrower for higher order quasi-confined modes. The strain effect of QW structures has a clear influence on the dispersion behavior of the quasi-confined phonon modes and improves the frequency of the quasi-confined phonons.

First-principles study on the dielectric and transport properties of the LiNbO3-type CdPbO3

2017 ◽  
Vol 31 (05) ◽  
pp. 1750032
Author(s):  
Jing Zhang ◽  
San Huang Ke ◽  
Derwyn A. Rowlands
Keyword(s):  
Transport Properties ◽  
First Principles ◽  
Electronic Devices ◽  
Differential Resistance ◽  
Uniaxial Crystal ◽  
Dielectric Constants ◽  
First Principles Calculation ◽  
Electric Transport ◽  
Phonon Modes ◽  
Ir And Raman

Using first-principles calculation method, we have investigated the zone-center phonon modes, dielectric and transport properties of the LiNbO3-type CdPbO3. The results show that the relatively large peaks of infrared (IR) and Raman spectra mainly come from the [Formula: see text] and [Formula: see text] modes, respectively. The dielectric constant calculations reveal that this compound is positive uniaxial crystal and has the large dielectric constants. By investigating the electric transport properties using gold as electrode, the interesting negative differential resistance (NDR) effect can be observed, which reveals this compound should have important application in semiconducting electronic devices.

scholarly journals Многократное изменение электрон-фононного взаимодействия в квантовых ямах с диэлектрически различными барьерами

2022 ◽  
Vol 56 (1) ◽  
pp. 101
Author(s):  
А.Ю. Маслов ◽  
О.В. Прошина
Keyword(s):  
Quantum Wells ◽  
Charged Particles ◽  
Strong Interactions ◽  
Asymmetric Structure ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Barrier Materials ◽  
Electron Phonon Interaction ◽  
Order Of Magnitude

Abstract The specific features of the interaction of charged particles with polar optical phonons have been studied theoretically for quantum wells with the barriers that are asymmetric in their dielectric properties. It is shown that the interaction with interface phonon modes makes the greatest contribution in narrow quantum wells. The parameters of the electron-phonon interaction were found for the cases of different values of the phonon frequencies in the barrier materials. It turned out that a significant (by almost an order of magnitude) change in the parameters of the electron-phonon interaction can occur in such structures. This makes it possible, in principle, to trace the transition from weak to strong interactions in quantum wells of the same type but with different compositions of barrier materials. The conditions are found under which an enhancement of the electron-phonon interaction is possible in an asymmetric structure in comparison with a symmetric one with the barriers of the same composition.

scholarly journals Localized surface plasmons in structures with linear Au nanoantennas on a SiO2/Si surface

2016 ◽  
Vol 7 ◽  
pp. 1519-1526 ◽  
Author(s):  
Ilya A Milekhin ◽  
Sergei A Kuznetsov ◽  
Ekaterina E Rodyakina ◽  
Alexander G Milekhin ◽  
Alexander V Latyshev ◽  
...  
Keyword(s):  
Penetration Depth ◽  
Surface Plasmons ◽  
Infrared Absorption ◽  
Transmission Spectra ◽  
Localized Surface Plasmons ◽  
Optical Phonons ◽  
Infrared Transmission ◽  
Phonon Modes ◽  
Electromagnetic Simulations

The study of infrared absorption by linear gold nanoantennas fabricated on a Si surface with underlying SiO2 layers of various thicknesses allowed the penetration depth of localized surface plasmons into SiO2 to be determined. The value of the penetration depth derived experimentally (20 ± 10 nm) corresponds to that obtained from electromagnetic simulations (12.9–30.0 nm). Coupling between plasmonic excitations of gold nanoantennas and optical phonons in SiO2 leads to the appearance of new plasmon–phonon modes observed in the infrared transmission spectra the frequencies of which are well predicted by the simulations.

POLAR VIBRATION SPECTRA OF INTERFACE AND SURFACE OPTICAL PHONONS AND THEIR FRÖHLICH ELECTRON-PHONON INTERACTIONS IN FREESTANDING SYMMETRICAL AND ASYMMETRICAL WURTZITEGaN/Ga1-xAlxNMULTI-LAYER HETEROSTRUCTURES

2006 ◽  
Vol 20 (05) ◽  
pp. 559-578 ◽  
Author(s):  
LI ZHANG ◽  
JUN-JIE SHI
Keyword(s):  
Quantum Wells ◽  
Electrostatic Potential ◽  
Uniaxial Crystal ◽  
Wave Number ◽  
Phonon Modes ◽  
Electron Phonon Interaction ◽  
Surface Optical ◽  
Electron Phonon Coupling ◽  
Crystal Model ◽  
Dielectric Continuum

Under the dielectric continuum model and Loudon's uniaxial crystal model, by adopting the transfer matrix method, the dispersion properties of the interface optical (IO) and surface optical (SO) phonon modes and their couplings with electrons in multi-layer coupling wurtzite quantum wells (QWs) are deduced and analyzed via the method of electrostatic potential expanding. Numerical calculations on a freestanding symmetrical wurtzite QW and an asymmetrical wurtzite QW have been performed. Results reveal that, in general, there are four branches of IO and two branches of SO phonon modes in the systems. The dispersions of these IO and SO phonon modes are obvious only when the free two-dimensional phonon wave number ktparallel to the heterostructure interfaces is small. The degenerating behavior for these phonon modes has been clearly observed for small kt. When ktis relatively large, with the increase in kt, the frequencies of the IO and SO phonon modes converge to some definite limiting frequencies in corresponding wurtzite single planar heterostructure. This feature have been analyzed in depth from the mathematical and physical viewpoints. The calculations of electron-phonon coupling function show that, the electrostatic potential distribution of the IO and SO mode in freestanding symmetrical wurtzite QW is either symmetrical or is antisymmetrical; but that in freestanding asymmetrical wurtzite QW is neither symmetrical nor is antisymmetric. The calculation also shows that the SO modes and the short wavelength phonon modes play a more important role in the electron-phonon interaction.

POLAR INTERFACE-OPTICAL VIBRATIONAL SPECTRA IN A WURTZITE GaN/AlN RECTANGULAR QUANTUM WIRE

2006 ◽  
Vol 13 (01) ◽  
pp. 75-80 ◽  
Author(s):  
L. ZHANG
Keyword(s):  
Quantum Wells ◽  
Quantum Wire ◽  
Quantum Wires ◽  
Uniaxial Crystal ◽  
Wave Number ◽  
Phonon Modes ◽  
Crystal Model ◽  
Limited Frequency ◽  
Dielectric Continuum ◽  
Dielectric Continuum Model

Under the dielectric continuum model and Loudon's uniaxial crystal model, the interface optical (IO) phonon modes in a quasi-one-dimensional (Q1D) wurtzite rectangular quantum wire are deduced and analyzed. Numerical calculation on a wurtzite GaN/AlN rectangular wurtzite quantum wire was performed. Results reveal that the dispersion frequencies of IO modes sensitively depend on the geometric structures of the Q1D wurtzite rectangular quantum wires. The degenerating behavior of the IO phonon modes in the Q1D wurtzite rectangular quantum wire has been clearly observed for small free wave number kz in z-direction. The limited frequency behaviors of IO modes have been analyzed deeply, and detailed comparisons with those in wurtzite planar quantum wells and cylindrical quantum wires are also done. Moreover, once the anisotropy of the wurtzite material has been ignored, the present theories can be naturally reduced to the situation of Q1D cubic rectangular quantum wire systems.

Monte Carlo Study of Phonon Heat Conduction in Silicon Thin Films Including Contributions of Optical Phonons

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Arpit Mittal ◽  
Sandip Mazumder
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Monte Carlo ◽  
Heat Conduction ◽  
Phonon Scattering ◽  
Computational Domain ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Silicon Thin Film ◽  
Silicon Thin Films

Abstract The Monte Carlo method has found prolific use in the solution of the Boltzmann transport equation for phonons for the prediction of nonequilibrium heat conduction in crystalline thin films. This paper contributes to the state-of-the-art by performing a systematic study of the role of the various phonon modes on thermal conductivity predictions, in particular, optical phonons. A procedure to calculate three-phonon scattering time-scales with the inclusion of optical phonons is described and implemented. The roles of various phonon modes are assessed. It is found that transverse acoustic (TA) phonons are the primary carriers of energy at low temperatures. At high temperatures (T>200 K), longitudinal acoustic (LA) phonons carry more energy than TA phonons. When optical phonons are included, there is a significant change in the amount of energy carried by various phonons modes, especially at room temperature, where optical modes are found to carry about 25% of the energy at steady state in silicon thin films. Most importantly, it is found that inclusion of optical phonons results in better match with experimental observations for silicon thin-film thermal conductivity. The inclusion of optical phonons is found to decrease the thermal conductivity at intermediate temperatures (50–200 K) and to increase it at high temperature (>200 K), especially when the film is thin. The effect of number of stochastic samples, the dimensionality of the computational domain (two-dimensional versus three-dimensional), and the lateral (in-plane) dimension of the film on the statistical accuracy and computational efficiency is systematically studied and elucidated for all temperatures.

Interaction of Isotopic Modes with Polaritons

1974 ◽  
Vol 29 (7) ◽  
pp. 1017-1022
Author(s):  
W. Nitsch ◽  
R. Claus
Keyword(s):  
Experimental Data ◽  
Aqueous Solutions ◽  
Dispersion Theory ◽  
Phonon Modes ◽  
Frequency Shifts ◽  
First Order

Weak phonon modes at 2032,5; 2040; 2046; and 2053cm-1 in K3Cu(CN)4 have been assigned to originate from 13C≡14N and 12C≡15N vibrations. The assignments have been carried out using measurements at He-temperatures and in aqueous solutions. Furthermore calculations have been used concerning the frequency shifts and relative intensities with respect to the 12C≡14N vibrations. The coupling of polariton modes associated with the A1-phonon at 2074 and the E-phonon at 2080 cm-1 with the isotopic modes has been experimentally investigated. A comparison of calculated dispersion branches with the experimental data has shown that the isotopic modes can not simply be treated as fundamentals because the coupling observed is much weaker than expected from the general polariton dispersion theory for first order phonons.

scholarly journals Birefrince Characteristics of an Optical Element

2019 ◽  
Vol 8 (9S3) ◽  
pp. 801-803
Keyword(s):  
Phase Difference ◽  
Optical Element ◽  
Uniaxial Crystal ◽  
Optic Axis ◽  
Intensity Measurement ◽  
Double Refraction ◽  
Varying Thickness

Phase difference variation in uniaxial crystal is investigated for varying thickness. Using double refraction property and optic axis method leads to the intensity measurement. The periphery example got when a unique (or focalized) shaft experiences an example of birefringent gem between two polarizers contains data which is intrinsic of the crystalline example under examination.

Conical extinction curves: a new universal stage technique

1964 ◽  
Vol 33 (265) ◽  
pp. 853-867 ◽  
Author(s):  
N. Joel ◽  
F. E. Tocher
Keyword(s):  
Uniaxial Crystal ◽  
Optic Axis ◽  
Circular Cone ◽  
Biaxial Crystal ◽  
Universal Stage

SummaryNew generalized extinction curves, derived from wave-normals located on a circular cone, are presented. They may be used with the universal stage for the accurate location of up to all three of the indicatrix axes, α, β, γ, of any biaxial crystal, or the optic axis of any uniaxial crystal.

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